kafkareceiver: Improve internal telemetry

[1pkg]

Description

This PR adds the following internal telemetry metrics to improve the receiver telemetry to make it easier to operate.

Click to expand

Name	Description	Type
kafka_receiver_bytes	The number of received bytes, accounting for client compression	sum
kafka_receiver_bytes_uncompressed	The number of received uncompressed bytes	sum
kafka_receiver_latency	Time it took to receive a batch of records	histogram
kafka_broker_connects	The number of connections opened	sum
kafka_broker_disconnects	The number of connections closed	sum
kafka_broker_throttling_duration	The throttling duration imposed by the broker when receiving records	histogram

Link to tracking issue

Fixes

#40816

Testing

Unit tests are updated and tested manually.

Documentation

Documentation is autogenerated with mdatagen.

[axw]

Thanks! Looks good. There are a couple of breaking changes here, we'll need to be clear about that in the changelog.

[axw]

This would be a breaking change. For the receiver we should either add a new "records" metric and keep the "messages" one but deprecate it; or alternatively update the exporter to use "messages" instead of "records". Sorry, I forgot we had this one.

I'd probably update the exporter metric for now, and we could deprecate/rename later. WDYT?

[1pkg]

I'm okay with either options, I agree that using records should be more "correct" way to call the metric. But if the preferred way is to introduce less breaking changes I will update the exporter PR to use messages for the metric name.

[1pkg]

I updated both the receiver and the exporter PRs to use consistent naming for messages to not cause any more breaking changes for now. Please take a look.

[axw]

Looks great. Thank you!